it doesn't complain when you spend too much time riding, hanging out with friends, skateboarding, etc.

you don't have to call your bike and pretend to care about how it's day was.

you don't have to pay for your bike's dinner, movie ticket, christmas/valentine's day present.

your bike doesn't guilt trip or manipulate you to try to get what it wants.

you don't have to cuddle with your bike after riding it (sorry pistaboy, that one was dirty).

your bike's parents won't get pissed at you over drama.

your bike won't turn into best friends with all of the friends you introduce it to.

other guys probably won't hit on your bike, and if they do, your bike won't talk back.

your bike actually likes exercising.

if you're on this forum, chances are your bike probably matches better than what your girlfriend is wearing.

and on and on and on and on...